In the interest of highway safety, it has been suggested that highway signs, utility poles and the like should be so constructed that damage to a vehicle and its passengers upon impact with an obstruction be minimized as much as possible. For this purpose, various types of breakaway couplings and yieldable supports for signs and posts have been suggested as exemplified by U.S. Pat. Nos. 2,961,204 and 3,521,917.
A further and more sophisticated breakaway coupling assembly is shown and described in applicant's U.S. Pat. No. 3,637,244. The construction of this patent has proven highly successful in extended tests by the New Jersey State Highway Department and has now been approved for use on New Jersey highways and elsewhere.
While the functioning of the device of said patent is very satisfactory it is found in practice that it presents many difficult problems in production, maintenance and installation. Thus, the numerous parts of the assembly are expensive to manufacture and require accurate casting and machining to close tolerances in order to assure proper functioning thereof. As pointed out in the example cited in said patent, a variation of as little as 0.01 foot in the positioning of the load concentrating element with respect to the breakaway coupling axes will significantly alter the operation of the assembly. Accordingly in allowing sufficient dimensional clearances in each of the various parts to permit ready assembly thereof, the load concentrating elements may be displaced or disoriented with respect to the breakaway coupling elements sufficient distances to significantly reduce or defeat the effectiveness of the assembly.
Furthermore, since at least four, and generally eight or more identical washers are used, and must be arranged with the load concentrating element of each washer positioned on the inner side of the breakaway coupling, there is always a danger that one or more of the washers will be installed improperly by a workman who does not fully understand the operation of the assembly. Thus one or more washers may be inverted or oriented with the load concentrating element located on the outer side of the breakaway coupling. If this should occur, the assembly will function improperly and may defeat the very purpose for which it is provided.